从上周开始,我就一直在想办法解决这个问题。好的,所以我需要在Swift中使用以下代码应用一些约束到UIView:

var new_view:UIView! = UIView(frame: CGRectMake(0, 0, 100, 100));
new_view.backgroundColor = UIColor.redColor();
view.addSubview(new_view);

var constX:NSLayoutConstraint = NSLayoutConstraint(item: new_view, attribute: NSLayoutAttribute.CenterX, relatedBy: NSLayoutRelation.Equal, toItem: self.view, attribute: NSLayoutAttribute.CenterX, multiplier: 1, constant: 0);
self.view.addConstraint(constX);

var constY:NSLayoutConstraint = NSLayoutConstraint(item: new_view, attribute: NSLayoutAttribute.CenterY, relatedBy: NSLayoutRelation.Equal, toItem: self.view, attribute: NSLayoutAttribute.CenterY, multiplier: 1, constant: 0);
self.view.addConstraint(constY);

var constW:NSLayoutConstraint = NSLayoutConstraint(item: new_view, attribute: NSLayoutAttribute.Width, relatedBy: NSLayoutRelation.Equal, toItem: new_view, attribute: NSLayoutAttribute.Width, multiplier: 1, constant: 0);
self.view.addConstraint(constW);

var constH:NSLayoutConstraint = NSLayoutConstraint(item: new_view, attribute: NSLayoutAttribute.Height, relatedBy: NSLayoutRelation.Equal, toItem: new_view, attribute: NSLayoutAttribute.Height, multiplier: 1, constant: 0);
self.view.addConstraint(constH);

但是Xcode返回了这个奇怪的输出:

2014-10-03 09:48:12.657 Test[35088:2454916] Unable to simultaneously satisfy constraints.  Probably at least one of the constraints in the following list is one you don't want. Try this: (1) look at each constraint and try to figure out which you don't expect; (2) find the code that added the unwanted constraint or constraints and fix it. (Note: If you're seeing NSAutoresizingMaskLayoutConstraints that you don't understand, refer to the documentation for the UIView property translatesAutoresizingMaskIntoConstraints) 
(
"<NSLayoutConstraint:0x7fa4ea446830 UIView:0x7fa4ea429290.centerX == UIView:0x7fa4ea4470f0.centerX>",
"<NSAutoresizingMaskLayoutConstraint:0x7fa4ea4516c0 h=--& v=--& UIView:0x7fa4ea429290.midX == + 50>",
"<NSLayoutConstraint:0x7fa4ea452830 'UIView-Encapsulated-Layout-Width' H:[UIView:0x7fa4ea4470f0(375)]>",
"<NSAutoresizingMaskLayoutConstraint:0x7fa4ea446db0 h=-&- v=-&- 'UIView-Encapsulated-Layout-Left' H:|-(0)-[UIView:0x7fa4ea4470f0]   (Names: '|':UIWindow:0x7fa4ea444b20 )>"
)

Will attempt to recover by breaking constraint <NSLayoutConstraint:0x7fa4ea446830 UIView:0x7fa4ea429290.centerX == UIView:0x7fa4ea4470f0.centerX>

Make a symbolic breakpoint at UIViewAlertForUnsatisfiableConstraints to catch this in the debugger. The methods in the UIConstraintBasedLayoutDebugging category on UIView listed in
<UIKit/UIView.h> may also be helpful.

2014-10-03 09:48:12.658 Test[35088:2454916] Unable to simultaneously satisfy constraints.  Probably at least one of the constraints in the following list is one you don't want. Try this: (1) look at each constraint and try to figure out which you don't expect; (2) find the code that added the unwanted constraint or constraints and fix it. (Note: If you're seeing NSAutoresizingMaskLayoutConstraints that you don't understand, refer to the documentation for the UIView property translatesAutoresizingMaskIntoConstraints)
(
"<NSLayoutConstraint:0x7fa4ea44d160 UIView:0x7fa4ea429290.centerY == UIView:0x7fa4ea4470f0.centerY>",
"<NSAutoresizingMaskLayoutConstraint:0x7fa4ea451b30 h=--& v=--& UIView:0x7fa4ea429290.midY == + 50>",
"<NSLayoutConstraint:0x7fa4ea44cf00 'UIView-Encapsulated-Layout-Height' V:[UIView:0x7fa4ea4470f0(667)]>",
"<NSAutoresizingMaskLayoutConstraint:0x7fa4ea452700 h=-&- v=-&- 'UIView-Encapsulated-Layout-Top' V:|-(0)-[UIView:0x7fa4ea4470f0]  (Names: '|':UIWindow:0x7fa4ea444b20 )>"
)

Will attempt to recover by breaking constraint <NSLayoutConstraint:0x7fa4ea44d160 UIView:0x7fa4ea429290.centerY == UIView:0x7fa4ea4470f0.centerY>

Make a symbolic breakpoint at UIViewAlertForUnsatisfiableConstraints to catch this in the debugger. The methods in the UIConstraintBasedLayoutDebugging category on UIView listed in <UIKit/UIView.h> may also be helpful.

你能帮我吗? 非常感谢


当前回答

这个错误是由autoresizingmask自动创建的约束引起的,它们的创建是因为UIView属性translatesAutoresizingMaskIntoConstraints默认为true。

考虑使用BoxView来摆脱所有手工约束创建样板,并使您的代码简洁易读。用BoxView做布局是非常简单的:

boxView.items = [
   new_view.boxed.centerX().centerY().relativeWidth(1.0).relativeHeight(1.0)
]

其他回答

操场上多个视图的约束。

斯威夫特 3+

  var yellowView: UIView!
    var redView: UIView!

    override func loadView() {

        // UI

        let view = UIView()
        view.backgroundColor = .white

        yellowView = UIView()
        yellowView.backgroundColor = .yellow
        view.addSubview(yellowView)

        redView = UIView()
        redView.backgroundColor = .red
        view.addSubview(redView)

        // Layout
        redView.translatesAutoresizingMaskIntoConstraints = false
        yellowView.translatesAutoresizingMaskIntoConstraints = false
        NSLayoutConstraint.activate([
            yellowView.topAnchor.constraint(equalTo: view.topAnchor, constant: 20),
            yellowView.leadingAnchor.constraint(equalTo: view.leadingAnchor, constant: 20),
            yellowView.widthAnchor.constraint(equalToConstant: 80),
            yellowView.heightAnchor.constraint(equalToConstant: 80),

            redView.bottomAnchor.constraint(equalTo: view.bottomAnchor, constant: -20),
            redView.trailingAnchor.constraint(equalTo: view.trailingAnchor,constant: -20),
            redView.widthAnchor.constraint(equalToConstant: 80),
            redView.heightAnchor.constraint(equalToConstant: 80)
            ])

        self.view = view
    }

在我看来,xcode游乐场是学习加法最好的地方 通过编程方式约束。

我们可以很容易地在swift 5.1中做到这一点

设置1

子视图对齐到视图中心 子视图宽度高度设置使用浮动 view.addSubview (myView1) myView1。translatesAutoresizingMaskIntoConstraints = false NSLayoutConstraint.activate ([ myView1.centerXAnchor。约束(等于:view.centerXAnchor), myView1.centerYAnchor。约束(等于:view.centerYAnchor), myView1.widthAnchor。约束(equalToConstant: 100), myView1.heightAnchor。约束(equalToConstant: 100), ])

设置2

subview align to view leading and top anchor subview width set using view width height view.addSubview(myView2) myView2.translatesAutoresizingMaskIntoConstraints = false NSLayoutConstraint.activate([ myView2.leadingAnchor.constraint(equalTo: view.leadingAnchor,constant: 16), myView2.topAnchor.constraint(equalTo: view.safeAreaLayoutGuide.topAnchor,constant: 16), myView2.widthAnchor.constraint(equalTo: view.widthAnchor, multiplier: 0.3), myView2.heightAnchor.constraint(equalTo: view.heightAnchor, multiplier: 0.3) ])

您可以使用Snapkit以编程方式设置约束。

class ViewController: UIViewController {
    
    let rectView: UIView = UIView(frame: CGRect(x: 0, y: 0, width: 100, height: 100))
    
    override func viewDidLoad() {
        super.viewDidLoad()
        setupViews()
    }
    
    private func setupViews() {
        rectView.backgroundColor = .red
        view.addSubview(rectView)

        rectView.snp.makeConstraints {
          $0.center.equalToSuperview()
        }
    }
}

这个错误是由autoresizingmask自动创建的约束引起的,它们的创建是因为UIView属性translatesAutoresizingMaskIntoConstraints默认为true。

考虑使用BoxView来摆脱所有手工约束创建样板,并使您的代码简洁易读。用BoxView做布局是非常简单的:

boxView.items = [
   new_view.boxed.centerX().centerY().relativeWidth(1.0).relativeHeight(1.0)
]

Swift 3更新

import UIKit

class ViewController: UIViewController {

let redView: UIView = {

    let view = UIView()
    view.translatesAutoresizingMaskIntoConstraints = false
    view.backgroundColor = .red
    return view
}()

override func viewDidLoad() {
    super.viewDidLoad()

    setupViews()
    setupAutoLayout()
}

func setupViews() {

    view.backgroundColor = .white
    view.addSubview(redView)
}

func setupAutoLayout() {

    // Available from iOS 9 commonly known as Anchoring System for AutoLayout...
    redView.leftAnchor.constraint(equalTo: view.leftAnchor, constant: 20).isActive = true
    redView.rightAnchor.constraint(equalTo: view.rightAnchor, constant: -20).isActive = true

    redView.centerYAnchor.constraint(equalTo: view.centerYAnchor).isActive = true
    redView.heightAnchor.constraint(equalToConstant: 300).isActive = true

    // You can also modified above last two lines as follows by commenting above & uncommenting below lines...
    // redView.topAnchor.constraint(equalTo: view.topAnchor, constant: 20).isActive = true
    // redView.bottomAnchor.constraint(equalTo: view.bottomAnchor).isActive = true
 }
}

约束的类型

 /*
// regular use
1.leftAnchor
2.rightAnchor
3.topAnchor
// intermediate use
4.widthAnchor
5.heightAnchor
6.bottomAnchor
7.centerXAnchor
8.centerYAnchor
// rare use
9.leadingAnchor
10.trailingAnchor
etc. (note: very project to project)
*/